File band



March 27, 1945. coDDlNG-roN 2,372,553

FILE BAND Filed June 11, 1942 iigiu'hand files.

` Patented Mar. 27, 1945 Iby direct and mesne. assignments, toContinental Machines, Incorporated,.Minneapolis,

Minn., a corporation of Minnesota" Application June 11, 1942, Serial No.446,640 3 claims. (C1. e9-fis) My present invention relates to toothedflexible band files and to novel methods of producingsuch toothedflexible band files, The band illes of the present invention are adaptedto be made'endless to run over pulleys or wheels in the manner of bandsaws and have hardened metal file teeth on the outer wide faces thereof,such teeth being rigid with and projecting directly fromthe underlyingflexible portion of the band.l These le bands, it should be understood,are of" the `forrned metal variety similar to the teeth of `:Bandfilesjmade in accordance with the present invention are relatively verythin so that they,

are adapted to be used in very narrow work openings, can be relativelyinexpensively 'produced, and have long iexure and cutting life.

Hitherto, such band files, as have been made available'commercially,have been made up of,I

flexible spring steel bands carrying on their outer wide surfaces aseriesof rigid file sections, each of which sections is similar to asection of a rigid hand le and which sections are laid end to end `witheach section anchoredl to the band permit independent iiexing of `thebands in one direction when running over wheels. or pulleys. ii'heseprior art Iiles have been difcult' and expensive to produce and haveotherwise been ob- Jectionable because of their essentially'high sales iprice, the excessive over-all thickness of the filesection-equippedbands making for difficulty for working in narrow work openings, theessential breaks in the filing surface between adjacent rigid lesections and the extreme likelihood of foreign substances collectingbetween the flexible bands and rigid Ifiling sections, resulting in mis-Y alignment of the filing surfaces of adjacent rigid filing sections.Although large numbers ofk such "atonlyone point longitudinally thereofso as to prior art file bandshavebeen sold and used over ting life,provides a uniform unbroken iiling surface throughout the length of theband, and

which is generally devoid of the above noted and` file band that can beproduced at relatively low K,

cost, is so thin as to permit easy working in very `narrow Workopenings, has long ilexure and cutother objections inherent in prier artfiling bandsof the type employing rigidle sections.

` "To this end I provide two forms of flexible file Abands in each ofwhich highly hardened file teeth are rigidly carried-directly by aflexible metal backing or supporting structure having a long ilexurelife. In one of these forms the band file teeth are formed directly inone wide face of the flexible metal band which forms the flexiblesupport for the teeth; but in the other form thereof, the band is acomposite structure comprising an inner flexible metal supporting bandhaving file teeth of different metal anchored fast to its wideo'utersurface. l l

\ The two forms of band illes of the present in- 'vention, together withvarious objects and adi vantages thereof and novel methods of producing`the same, will hereinafter be more fully described and denned inconnection with the accompanying drawing wherein like charactersindicate like parts throughout the several views.

Referring to the drawing:

i Fig. 1 is a fragmentary perspective view showing certain elements ofthe multiple ply or composite band structure in separated relation;

Fig. 2 is a view corresponding to Fig, 1 but showing the elements of theband iile forming structure united;

Fig. 3 is a fragmentary perspective view corresponding to Fig. 2 butillustrating the same after the file teeth have been formed in the outerlayer or ply of the band;

L: Fig. 4 is a fragmentary prespect'ive View of the single layer form ofband le and showing the same during the tooth forming operation;

Fig. 5 is a more or less diagrammatic view il- -lustrating an apparatusfor use in heat hardening f the file teeth in a completed endless fileband of either of the forms of Figs. 1 to 3,y inclusive, or Fig. 4; A uFig. (i is a greatly enlarged fragmentary sectional view in sideelevation of a section of the completed le band of the type shown inFigs. 1 to 3, inclusive;

Fig. 7 is a View corresponding to Fig. 6 but showing the form of bandfile shown in Fig. 4;

. and

Fig. 8 is a fragmentary plan view showing how either form of iile bandWould appear if provided with intersecting rows of le teeth.

rlf'he partially completed band, `shown in Fig. 3, comprises a flexiblesupportingk band structure I0 having long ilexure life,. such as springsteel alloy used in band saws and the like, and to the vouter `Wide faceof which are rigidly anchored file teeth II which extend obliquely fromedge to edge of the band. In practice, however, and as 'will hereinafterbe made further apparent, the completed band, as shown in Fig. 8, willbe formed with intersecting rows of teeth II. The teeth II aremetallically bonded to the wide outer surface of the flexible supportingband I at I2 by suitable processes such as soldering, brazing, weldingor the like.

The teeth Il are preferably formed of alloy steel capable of hardeningto provide a long life cutting edge and high speed tool steel isconsidered highly satisfactory for this purpose.

The band file of Figs. 4 and '7 is a single layer structure in which thefile teeth IIa are formed in the outside wide portion of a flexiblesteel band IIIa. In this form of band iile, the band is made up of steelalloy which may be heat tempered to provide long life flexingcharacteristics or to provide a high quality cutting surface, and forthis purpose high carbon steel alloy is considered satisfactory.Preferably, that portion of the band Ilia of Fig. 7 lying below theteeth IIa may be assumed to be heat tempered to a spring temper, whereasthe outer cutting edges of the teeth may be assumed to be tempered toprovide a very hard cutting surface.

The preferred method of forming the band of Figs. 1 to 3, and 6, willnext be described. The first step in the method of producing thismultiple layer or composite file band structure comprises metallicallybonding together or uniting the flexible supporting band I0 with a toothforming outer band A in which the teeth II are subsequently to beformed. As previously indicated, the supporting strip or band IU will beof steel or other alloy providing long ilexure life such as high carbonspring steel, whereas the tooth forming outer ribbonlike band A will beof steel alloy providing the highest possible degree of cutting quality.Preferably, the uniting of the bands lil and A will be by silversoldering which can very readily be accomplished by interposing be`tween the bands I0 and A a very thing sheet of silver solder I2 and thenheating the bands I0 and A under pressure to the temperature required tofuse the solder and permanently bond the two layers. In practice, thisheating of the elements lil and A under pressure can veri7 readily bebrought about by passing the superimposed layers IG and A with theirinterposed strip of solder between heated pressure rollers so that thebonding is accomplished in a continuous operation. If silver solder orsimilar bonding agent having a similar low fusing point is used,the-bands or elements IU and A will not be heated to their criticaltemperatures and no tempering will result during the bonding process. Inthis case the band I9 may loe-initially tempered to provide the desiredilexing characteristics and the tooth forming layer A may be in acompletely vannealed state desirable for tooth forming and the temper ofneither thereof will be affected as a result of the bonding operation.However, if brazing or .welding is employed, to bond the layers I0 andA, slow cooling and consequent annealing of the elements will benecessary in order to restore the tooth forming layer A to a workingcondition and the supporting band Ill to a proper flexing condition.

When the bonding process has been completed, the united elements willappear as in Fig. 2.

The next step in forming the band file of Figs. 1 to 3, inclusive, and6, comprises forming in the annealed steel layer A the file teeth II,and this is preferably accomplished by cutting or milling groovesobliquely .across the layer Ato provide the teeth II. First the grooveswill be cut obliquely across the layer A in one direction, as shown inFig. 4, and then other tooth forming grooves will be similarly cutobliquely across the layer A in the opposite direction so as to provideintersecting rows of teeth, as shown in Fig. 8. It is desirable,however, that one, and preferably both, of tooth forming sets of groovesbe cut all or substantially lall the way through the layer A so that thebases of the teeth are substantially at the point of junction betweenthe bands Ill and A. Preferably also, the grooves; which form the teeth,will be round bottomed so as to reduce the tendency to start cracks. Theforming of the teeth II by milling or cutting is greatly preferred overstamping or chisel cutting, since these latter processes tend tofracture the underlying metal which would greatly shortenfthe flexinglife of the unit, whereas cutting produces no fractures or otherinjuries.

The next step in the process of forming the band of Figs. l to 3,inclusivey and 6, comprises hardening the teeth II and this ispreferably accomplished by flame hardening which consists in heating theteeth II by direct application of heat thereto and then rapidly coolingthe band to prevent penetration of the heat into the underlyingsupporting band IIJ to such an extent as to raise its temperature beyondthe critical point and thereby affect its temper. This hardening ortempering of the teeth is preferably accomplished by flame hardeningthrough the medium of an apparatus such as exemplified in Fig. 5,wherein a completed band file has its ends joined to provide an endlessband yand is run over a pair of wheels or pulleys I3 that areindependently journaled on a supporting structure I4.

The lower of these wheels I3 runs in a tank I5 wherein cooling orquenching water is maintained to the level established by a drain pipeI6. The wheels I3 may be assumed to be driven at a predetermined speedand while they are turning a tempering ame y is applied to the teeth IIas the teeth move there passed. Gas is fed to the iiame y through asuitable pipe I1 and nozzle I8 and the flame and speed of travel of theband are controlled to provide the desired degree oi heating of theteeth.

For immediately cooling the teeth to thereby harden the same and preventfurther penetration of heat into the band, a stream of quench water a:is projected onto the toothed surface' of the band in close relation tothe ame y. Quench water is supplied through a nozzleequipped pipe I9 andthis water runs into the tank and maintains a constant flowtherethrough.

Since the bottom of the -lower wheel I3 runs in the quenching water,this wheel will be maintained in a cool condition so that it rapidlydissipates heat rfrom the band under the action of the name, and forthisV reason the flame is preferably applied at a point where the fileband is in contact with the lower wheel. Of course, the sharp ends ofthe teeth will become vmuch harder than the wide base portions thereofduring the brief heating period and after the band has passed throughthe f quench,` the ends of the teeth will be very hard and the degree ofhardness will rapidly fade off toward the base of the teeth until at thebase the teeth may be very little, if any, above the normal annealedcondition thereof. This varying degreel of .hardness is illustrated inFig. 6 by dot shading.

The darkly shaded area at the tips of the teeth Il indicates anextremely high degree of hardness, whereas the lightly shaded areas atthe bases of the teeth indicate a substantially unhardened condition.

Two slightly different methods of producing the form of band file shownin Figs. 4 and 7 will now be described. The first step in either ofthese methods consists Vin forming in the single layer` bandla the'teethIla, which teeth are preferably formed by cutting or milling groovesobliquely across the outer surface of the band Hla to form long teeth Il a, as shown in Fig. 4, after which a second set of grooves Will be cutobliquely across the same surface of the band Illa at the opposite angleso as to form intersecting rows of file teeth just as in Fig. 8. Theteeth Ha are out in the band I a while the band Illa, which ispreferably of high carbon steel alloy, is in an annealed state. Inaccordance with one of the two methods of producing the finished band ofthe type shown in Figs. 4 and 7, I flame harden the teeth While the banda is in an annealed state and accomplish this just as previouslydescribed in connection with the multiple layer band and through the useof the apparatus disclosed in Fig. 5. In doing this the tips of theteeth lla are heated to a high temperature and then rapidly quenched bythe water stream or spray a: so that the hardness fades off toward thebase of the teeth to the point where the bases of the teeth ila remainsubstantially in an annealed state.

The other, and perhaps preferred method of completing the band of Figs.4 and 7, comprises tempering the toothed band I0a to a spring temperwhich will provide the greatest possible degree of flexure life, andthen subsequently name hardening the teeth in the manner previouslydescribed and wherein the water spray cools the teeth before the heathas penetrated the supporting underlying portion of the band Illa suf-vficiently to materially affect its spring tempered condition..

In connection with the form of band shown in Figs. 4 and '7, it isparticularly important that the groovesithat form the teeth be wellrounded at their bases so as to reduce to a maximum the tendency tostart ilexure cracks, and it is also important that the tooth temperingheat be quenched before the critical temperature is reached in this areanear the bases of the teeth.

In the form of band shown in Figs. 1 to 3, inclusive, and 6, the outerlayer A of the band, in which the teeth are formed, comprises what mayhereinafter be referred to as a strata capable of hardening to cuttingtemper or hardness, and the underlying layer I0 constitutes strataadapted to be heat treated to provide high exing qualities. In the formof band shown particularly in Figs. f1 and 7, that portion of the bandwherein the teeth lla are out, or at least the outer portion thereof,constitutes a strata adapted to be tempered to cutting hardness, Whereasthat portion of the band underlying the teeth constitutes a strataadapted to be tempered to give desired flexing qualities, and this istrue even when theentire band I0@ is compounded ofthe same alloy. s

Of course, if the finished band is to have long flexure life, there mustbe a reasonable degree of flexibility in the teeth themselves and forthis reason the fading off of the hardness of the teeth from their tipstoward their bases is highly important, for when hardened as above described and indicated in Figs. e and 7, the bases ing strip of thinflexible metal adapted to be trained over the pulleys of an endless bandtype filing machine; a facing strip of thin metal capable of beinghardened; and means permanently securing the strips flatwise together;said facing strip having tooth forming grooves cut in its outer surfaceto a depth substantially equal to the thickness of the facing strip sothat the teeth of the file band are relatively independent and connectedto one another primarily through said securing means and the flexiblebacking strip, and said file teeth being hardened.

2. A flexible le band of the character described comprising: anelongated endless backing strip of thin flexible material adapted to betrained over the pulleys of an endless band type ling machine; andhardened individual iile teeth originally independent from the backingstrip, each permanently banded to one face of the backing strip with theteeth in closely spaced relationship to form an abrading surface on theband.

3. A flexible flle band of the character described comprising: anelongated endless backing strip of thin spring steel adapted to betrained over the pulleys of an endless band type filing machine; and afacing strip of relatively thin metal permanently bonded to the backingstrip and having closely spaced tooth forming grooves cut in its outersurface to a depth substantially equal to the thickness of the facingstrip so as to insure flexibility of the file band.

LLOYD CODDINGTON.

